WEATHERAmerica Newsletter, MEDIUM RANGE OUTLOOK, Saturday, August 9, 2025

[Larry Cosgrove]

MEDIUM RANGE OUTLOOK

(Four To Ten Days From Now)

 

Thunderstorms Mainly West And North, Lots Of Heat, Humidity Elsewhere....

UQAM Meteocentre (4)

TrueWx.Com (4)

TwisterData.Com (4)

College Of DuPage Weather Laboratory

Model guidance shows that another surge of monsoonal moisture from the equatorial Pacific Ocean will move up through Mexico into the Southwest in the medium range, while a cold front from the Gulf of Alaska pushes into the Pacific Northwest and through the Prairie Provinces . Temperature trends are mostly higher from the Great Plains and Texas through the Midwest, Dixie and the Eastern Seaboard. The proviso is that where diurnal convection erupts, truly extreme heat may be lessened somewhat (albeit with very steamy night temperatures). Keep in mind that if the subtropical high sets up like what the ECMWF version is showing, the area from Texas/Oklahoma to the Mid-Atlantic and the Southeast will deal with a brutal display of widespread 100 deg F and higher readings in the 6-10 day time frame.

....And Heat Ridge Position Will Determine Future Track Of Potential Tropical Cyclones

ECMWF (4)

PivotalWeather.Com (4)

Based on the most recent forecast model guidance, you would think that there are no dangers from a tropical cyclone strike into the USA. That may not be true, as two schemes indicate a real risk after this time frame to Florida/Texas (ECMWF/AI) or New England (GEFS Control) in the 11-15 day time frame. But one issue to deal with is what one would expect in August: heat. All of the series show an impressive heat ridge somewhere to the right of the Rocky Mountains and below the Interstate 80 corridor. The problem shaping up is the prospect of a weakness in the 500MB flow moving from the Florida Peninsula into Texas/Oklahoma. You may recall the early July set-up where the gap between ridges got stuck along the Interstate 35 corridor in the central TX counties. West-northwest flow aloft could ultimately give the Great Lakes and the Northeast at least a brief break from the cTw+mTw air mass. The ridging in the Great Plains and Dixie will be very dirty (see the pockmarked temperature depiction caused by clouds, haze and diurnal convection), but these maps have a very steady "hazy, hot and humid" look that should persist into the longer term.